What Humans Can Learn from Tadpoles: Regeneration of Lost Tissue

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Tadpoles, the initial form taken by young amphibians such as frogs and salamanders, have an extraordinary quality which sets them apart from mammals. They are able to regenerate their tails should they be eaten by a predator. If a tadpole loses its tail, it will grow a new one within a week! Imagine if a human can do that with an amputated limb. For several years, scientists have been studying the tadpole's regenerative tail, trying to understand the process, eventually leading to treatments and therapies that might help humans to heal their wounds.

Tadpoles, the initial form taken by young amphibians such as frogs and salamanders, have an extraordinary quality which sets them apart from mammals. They are able to regenerate their tails should they be eaten by a predator. If a tadpole loses its tail, it will grow a new one within a week! Imagine if a human can do that with an amputated limb. For several years, scientists have been studying the tadpole's regenerative tail, trying to understand the process, eventually leading to treatments and therapies that might help humans to heal their wounds.

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The researchers, led by Professor Enrique Amaya of the The Healing Foundation Centre in the Faculty of Life Sciences, had already identified the genes which are activated during the regeneration process. The genes they identified were involved in metabolism and are linked to the production of reactive oxygen species (ROS). These are chemically reactive molecules containing oxygen, widely believed to be harmful to cells.

It seemed strange that genes which produce harmful molecules could be instrumental in regenerating lost tissue. "We were very surprised to find these high levels of ROS during tail regeneration," said Professor Amaya. "Traditionally, ROS have been thought to have a negative impact on cells. But in this case they seemed to be having a positive impact on tail re-growth."

Their follow-up research focused on the ROS and resulted in some unexpected findings. Amaya's team tried to limit ROS production by both removing certain chemicals (including an antioxidant) from the tadpoles and by removing the gene found to be responsible for ROS production. Both methods stopped the regeneration process and the tadpoleâ€™s tail did not grow back.

"When we decreased ROS levels, tissue growth and regeneration failed to occur. Our research suggests that ROS are essential to initiate and sustain the regeneration response. We also found that ROS production is essential to activate Wnt signaling, which has been implicated in essentially every studied regeneration system, including those found in humans. It was also striking that our study showed that antioxidants had such a negative impact on tissue regrowth, as we are often told that antioxidants should be beneficial to health."

Further research is expected to focus on the reactive oxygen species (ROS) and how they can be applied in humans. The findings may have important implications in future regenerative medicine.